Immune Response Calculator

After vaccination, the immune system produces two main classes of antibody on different timelines. IgM appears first, typically rising to a peak around 7-10 days after exposure and then declining as IgG production ramps up -- this general sequence (IgM first, IgG following) is standard immunology, though the exact days vary by vaccine and individual. IgG is the longer-lasting, more specific antibody that provides durable protection, typically peaking around 2-3 weeks after a first (primary) dose. A second or later dose triggers a faster, stronger "anamnestic" response from memory B cells formed during the first exposure -- IgG rises faster and to a higher peak than after the primary dose, which is the immunological basis for booster schedules. This calculator models that general shape: it estimates relative IgM and IgG levels at a given number of days post-vaccination, adjusts for reduced immune responsiveness in patients over 65 (immune senescence) and in immunocompromised patients, and reports an estimated seroconversion probability and protection level.

Seroconversion probability ramps up from near 0% at day 0 -- since no antibody response has developed yet, seroconversion can't meaningfully have happened -- toward its full estimated ceiling as Days post-vaccination approaches the IgG peak day, then holds there; it does not report the eventual ceiling value from day 0 onward. Days to peak immunity matches the same peak-day timing this calculator's IgG curve actually uses, which is set by Dose number, not by age or immune status -- age and immunocompromised status scale how MUCH antibody is produced in this model, not WHEN the curve peaks. Dose number differentiates each of the five selectable doses (not just "dose 1 vs. everything else"): IgM's relative contribution wanes slightly with each additional booster as IgG memory response dominates, IgG peaks progressively faster with more prior exposures, and IgG's peak level rises with diminishing per-dose gains. This is an illustrative, simplified model of well-established immunology principles -- it is not a validated predictive tool calibrated to any specific vaccine's actual clinical trial data, and real antibody kinetics vary substantially by vaccine type, dose, and individual immune history. Use it to understand the general shape of a vaccine response, not to predict your own antibody level or protection status, which requires an actual lab test.